Abstract：
High accuracy analysis of linear triangular element is proposed for two-dimensional multi-term time fractional diffusion equations with Caputo fractional derivative on anisotropic meshes. Firstly, based on linear triangular element and modified L1 scheme, a fully-discrete approximate scheme is established and the unconditional stability analysis is investigated. Secondly, by use of the relationship between the interpolation operator and Riesz projection operator, superclose property is derived by related known high accuracy results. Moreover, the superconvergence estimate is obtained through the interpolation postprocessing technique. It is worth mentioning that the above superclose and superconvergence results will not be derived by the interpolation operator and Riesz projection operator alone. Finally, numerical results are provided to confirm the validity of our theoretical analysis. Furthermore, some popular finite elements of numerical approximation for the focused equation are investigated.